Late Quaternary seasonal process variations in lake basins on the NE Tibetan Plateau

Abstract The late Quaternary climate history along the north-eastern Tibetan Plateau (NETP) is still a matter of debate with respect to signals in lake deposits and related catchment processes. Here we summarize the current knowledge based on lake development and eolian accumulation in catchments on the NETP. Interlinked processes between selected lakes and their catchments on the NETP show a relatively clear division into summer and late autumn/winter/early spring (October to April) dominated activities based on lake hydrological and eolian variations. Investigated lakes on the NETP experienced seldom water cover or pond/playa status during the Late Glacial with long ice cover periods. Eolian sand deposited in lake beds and/or the eastern parts of the respective catchments as a constant process during the colder season. These processes continued during the early Holocene despite climate warming and increased moisture supply as lake levels still remained relatively low, mainly fed by spring/summer glacier and snow melt. Eolian sand activity dominated in the catchments during the cold periods, while coarse sediments in the lake centers were mainly deposited by fluvial input in spring/summer and/or randomly distributed eolian material in ice cracks after melt in spring. During the mid-Holocene high lake levels occurred due to intensified multiple moisture supply sources. Eolian sand accumulation diminished and was eroded by precipitation thus more fluvial suspension was transported to the lake center. Subsequently, lake level decline until around 3 ka BP signaled a reduction in moisture availability and related surface runoff. Eolian sediment was less preserved due to surface erosion in line with lake level increase during the succeeding period. Fluvial material mixed with eolian sand was transported to the lake center during unfrozen periods. Afterwards fluctuating lake levels and intensive eolian deposits were frequently documented for the last 2 ka demonstrating climate variations similar to present. Fluctuations between the Asian summer monsoon (ASM) and Mid Latitude Westerlies (MLW)/Asian winter monsoon (AWM) influences were recorded with respect to season shifts for the entire Holocene with general dominance of north-westerly surface winds at investigated sites. Inspected periodicities of one lake record and eolian material demonstrate that local effects are of significance for eolian accumulations however, both records react to regional/global climatic changes but with different extend.